Imagine you’re tasked with building the world’s lightest drone chassis—something strong enough to survive turbulence but light enough to fly longer. You’ve narrowed it down to magnesium alloys. But then comes the question… AZ31B or AZ91D? Which one do you choose?

This isn’t just a metal selection—it’s an engineering decision that affects cost, performance, and even your product’s environmental impact.

Let’s break down these two magnesium marvels.

The Basics: Wrought vs Cast Magnesium Alloys

Magnesium alloys fall into two main categories:

  • Wrought Alloys (e.g., AZ31B – UNS M11311): Formed via mechanical means like rolling or extrusion.
  • Cast Alloys (e.g., AZ91D – UNS M11916): Produced by pouring molten metal into molds.

Each category influences properties like strength, ductility, and application suitability.

Chemical Composition

ElementAZ31B (UNS M11311)AZ91D (UNS M11916)
Magnesium (Mg)93.6–97.1%88.7–91.2%
Aluminum (Al)2.4–3.6%8.3–9.7%
Zinc (Zn)0.5–1.5%0.35–1.0%
Manganese (Mn)0.05–1.0%0.15–0.5%
Others≤0.3%Minimal
AZ91D has a higher aluminum content, leading to better corrosion resistance and hardness—ideal for external and automotive components.

Mechanical & Thermal Properties

PropertyAZ31BAZ91D
Ultimate Tensile Strength (MPa)270160–220
Yield Strength (MPa)18080–130
Elongation at Break (%)8.32.3–4.5
Brinell Hardness50–7360–80
Thermal Conductivity (W/m-K)10078
Electrical Conductivity (% IACS)1811
Melting Point (°C)600490–600
Density (g/cm³)1.71.7
AZ31B is superior for ductility and thermal performance, while AZ91D leads in surface hardness and corrosion resistance.

Machinability & Formability

  • AZ31B: Rated as excellent. Best suited for prototyping, complex shapes, and precision work.
  • AZ91D:Very good machinability but shines in high-volume die-casting, ensuring dimensional stability and consistency.

Applications: Where They Shine

Major Applications of AZ31B

Aerospace Components: Lightweight structural parts such as brackets and panels are manufactured using AZ31B to reduce overall aircraft weight and improve fuel efficiency.

Industrial Applications: Commonly used in power tools and mechanical equipment where reduced weight improves operational ease.

Prototypes: Due to its machinability, AZ31B is favoured for rapid prototyping and proof-of-concept designs

Major Applications of AZ91D

Consumer Electronics: Frequently used for lightweight casings in laptops, smartphones, and cameras, combining strength and reduced weight.

Automotive Components: Widely applied in engine housings, transmission cases, and other parts where weight reduction is critical to vehicle efficiency.

Recreational Equipment: Utilized in the manufacturing of sporting goods such as bicycle frames and golf club heads for their lightweight and durable qualities.

Environmental Considerations

Though AZ91D has slightly more embodied water and carbon (22 kg CO₂/kg vs 23 for AZ31B), its superior corrosion resistance and durability lead to longer lifecycles, fewer replacements, and reduced environmental strain over time.

Sustainability Tip: Fewer replacements = less recycling energy + fewer emissions. If your product faces harsh conditions, AZ91D is your eco-friendlier choice in the long run.

Standards & Specifications

  • AZ31B:
    • ASTM B90/B90M
    • Available in: Plates, Sheets, Rods, Bars, Extrusions
    • Condition: H24 (strain-hardened & partially annealed)
  • AZ91D:
    • ASTM B93/B93M
    • Common as: Castings (Die Cast or Sand Cast)
    • Shape: Engine casings, electronic housings, intricate brackets

AZ31B vs AZ91D – Summary Table

FeatureAZ31B (Wrought)AZ91D (Cast)
ProcessExtrusion, RollingDie Casting
StrengthHigherModerate
DuctilityExcellentFair
Corrosion ResistanceModerateHigh
Best ForPrecision formingMass production
Cost-EffectivenessFor prototypesFor large batches
Conclusion: Which One to Choose?

If you’re aiming for precision, formability, and rapid prototyping, AZ31B is your go-to.
But for mass production, better corrosion resistance, and complex shapes, AZ91D outperforms over the long haul.
🔩 Whether you’re designing the next ultralight gadget or engineering tomorrow’s fuel-efficient vehicle, choosing the right magnesium alloy is a decision that shapes both performance and planet.

👉 Contact us now to explore custom solutions for your tech.

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